Add a shadow to the FloatingActionButton.

Also added a helper class to Sky framework for building shadow DrawLoopers.

R=abarth@chromium.org, eseidel@chromium.org, ianh@google.com

Review URL: https://codereview.chromium.org/1175683002.

sdk/BUILD.gn

@@ -99,6 +99,7 @@ dart_pkg("sdk") {
     "lib/framework/net/fetch.dart",
     "lib/framework/net/image_cache.dart",
     "lib/framework/node.dart",
+    "lib/framework/painting/shadows.dart",
     "lib/framework/reflect.dart",
     "lib/framework/rendering/block.dart",
     "lib/framework/rendering/box.dart",

sdk/lib/framework/components2/floating_action_button.dart

@@ -4,6 +4,7 @@
 
 import '../fn2.dart';
 import '../rendering/box.dart';
+import '../painting/shadows.dart';
 import '../theme2/colors.dart';
 import 'dart:sky' as sky;
 import 'ink_well.dart';
@@ -28,7 +29,13 @@ class FloatingActionButton extends Component {
       content: new CustomPaint(
         callback: (sky.Canvas canvas) {
           const double radius = _kSize / 2.0;
-          canvas.drawCircle(radius, radius, radius, new sky.Paint()..color = Red[500]);
+          sky.Paint paint = new sky.Paint()..color = Red[500];
+          var builder = new ShadowDrawLooperBuilder()
+            ..addShadow(const sky.Size(0.0, 5.0),
+                        const sky.Color(0x77000000),
+                        5.0);
+          paint.setDrawLooper(builder.build());
+          canvas.drawCircle(radius, radius, radius, paint);
         },
         child: new Container(
           width: _kSize,

sdk/lib/framework/painting/shadows.dart

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:sky' as sky;
+
+/// Helper class to build a Paint DrawLooper that adds shadows to the Paint's
+/// operation.
+class ShadowDrawLooperBuilder {
+  var builder_ = new sky.LayerDrawLooperBuilder();
+
+  void addShadow(sky.Size offset, sky.Color color, double blur) {
+    builder_.addLayerOnTop(
+          new sky.DrawLooperLayerInfo()
+            ..setPaintBits(-1)
+            ..setOffset(offset.toPoint())
+            ..setColorMode(sky.TransferMode.srcMode),
+          (sky.Paint layerPaint) {
+        layerPaint.color = color;
+        layerPaint.setMaskFilter(
+          new sky.MaskFilter.Blur(sky.BlurStyle.normal,
+                                  blur,
+                                  highQuality: true));
+      });
+  }
+
+  sky.DrawLooper build() {
+    builder_.addLayerOnTop(new sky.DrawLooperLayerInfo(), (_) {});
+    return builder_.build();
+  }
+}

sdk/lib/framework/rendering/box.dart

@@ -6,6 +6,7 @@ import 'dart:math' as math;
 import 'dart:sky' as sky;
 import 'dart:typed_data';
 import 'object.dart';
+import '../painting/shadows.dart';
 import 'package:vector_math/vector_math.dart';
 import 'package:sky/framework/net/image_cache.dart' as image_cache;
 
@@ -703,22 +704,9 @@ class RenderDecoratedBox extends RenderProxyBox {
         paint.color = _decoration.backgroundColor;
 
       if (_decoration.boxShadow != null) {
-        var builder = new sky.LayerDrawLooperBuilder();
-        for (BoxShadow boxShadow in _decoration.boxShadow) {
-          builder.addLayerOnTop(
-                new sky.DrawLooperLayerInfo()
-                  ..setPaintBits(-1)
-                  ..setOffset(boxShadow.offset.toPoint())
-                  ..setColorMode(sky.TransferMode.srcMode),
-                (Paint layerPaint) {
-              layerPaint.color = boxShadow.color;
-              layerPaint.setMaskFilter(
-                new sky.MaskFilter.Blur(sky.BlurStyle.normal,
-                                        boxShadow.blur,
-                                        highQuality: true));
-            });
-        }
-        builder.addLayerOnTop(new sky.DrawLooperLayerInfo(), (_) {});
+        var builder = new ShadowDrawLooperBuilder();
+        for (BoxShadow boxShadow in _decoration.boxShadow)
+          builder.addShadow(boxShadow.offset, boxShadow.color, boxShadow.blur);
         paint.setDrawLooper(builder.build());
       }